In recent years the concern that an excess of vitamin B12 can cause cancer has sparked quite a lot of debate in the medical community, and not just in professional settings. The increase in cancer risks was either attributed to vitamin B12 itself provided as a dietary supplement to those with anemia or other health issues requiring supplementation, or to carcinogenic compounds found in foods naturally high in vitamin B12 such as red meat.
But is it vitamin B12 that really causes cancer, or an increase in the risk of developing certain cancers, or is it other cancer-causing agents found in foods naturally containing vitamin B12 or in vitamin B12 supplements? Is there any research to indicate a correlation between vitamin B12 and an increased risk of cancer? And which cancers? Is vitamin B12 a cancer cure or risk?
Can vitamin B12 cause cancer?
At this point in time, there is no solid, conclusive research to show, without a doubt, that a high intake or high levels of vitamin B12 can cause cancer or increase risks of the disease. This being said, in a thin database cohort study on 757,185 persons, elevated plasma B12 levels were associated with a higher 1-year cancer risk than normal B12 levels. The risks were higher for liver and pancreas cancer, and myeloid malignancies among persons with elevated B12 levels (study 1).
In a long-term follow-up study on folic acid and vitamin B12 supplementation for the prevention of osteoporosis fractures and the risk of cancer, results showed folic acid and vitamin B12 supplementation to be associated with an increased risk of cancer, colorectal cancer in particular (study 2).
It is however unclear at this point whether vitamin B12 itself increases risks of certain forms of cancer, or if certain predispositions, risk factors, existing imbalances or diseases, diagnosed or not, predispose to high levels of vitamin B12 which are then mistaken for the cause of said diseases.
Another study showed an increased risk for lung cancer, overall and by histological subtype, per increase in circulating vitamin B12 concentrations indicating that high levels of vitamin B12 may potentially carry a higher risk for lung cancer. Further analysis also indicated that genetically determined higher vitamin B12 concentrations were positively associated with overall lung cancer risk, further supporting the hypothesis that high vitamin B12 status increases the risk of lung cancer (study 3).
An abnormally high vitamin B12 blood level is believed by some researchers to constitute a warning sign as to the potential for a hidden pathology, whether cancer, liver disease, kidney disease or something else. If you have abnormally high blood levels of vitamin B12, it is important to see your doctor and together investigate potential causes to exclude serious underlying conditions or get timely diagnosis and treatment. At the same time, it is important to understand that further confirmation is needed in larger studies to accurately assess whether or not vitamin B12 can cause or increase the risk for certain forms of cancer.
Vitamin B12: not a carcinogen?
Research does not reveal vitamin B12 as a carcinogen, that is, a cancer-causing agent. If anything, vitamin B12 is an essential dietary nutrient, one without which the human body cannot do. So how is it possible that studies link high levels of circulating vitamin B12 to an increased risk of certain cancers? Is it possible that vitamin B12 is not the reason behind the higher incidence of cancer observed in people with high blood levels of vitamin B12? Possibly.
For one, there is no research to definitively prove that vitamin B12 is a carcinogen. Secondly, studies that have linked high vitamin B12 blood levels to increased risks of certain cancers have only correlated the high vitamin B12 levels and the higher cancer risk based on a pattern of co-occurrence. Vitamin B12 has not been identified as a cause, but rather as a marker that indicates the need to investigate a potential pathology, cancer or another.
Thirdly, high blood levels of vitamin B12 do not occur in otherwise healthy individuals who meet their nutritional requirements from a varied and balanced diet, and maybe only occasionally supplement to account for minor losses due to stress, menses, childbirth, nosebleeds, minor wounds or other causes asking for temporarily increased dietary requirements.
High blood levels of vitamin B12 tend to occur as a result of supplementation in individuals with severe deficiencies of the vitamin. And severe vitamin B12 deficiencies have big causes such as anemia, surgery (gastric bypass, removal of part of the stomach or GI tract, possibly due to malignancies), chronic diseases, genetic disorders, certain medication, including anticancer medication and antibiotics, but also malnutrition and cancer.
The root cause of high blood levels of vitamin B12 can also be the cause for the increased risk of cancer observed, or an underlying, undiagnosed cancer can potentially cause the deficiency that requires supplementation to raise blood levels of the vitamin. For instance, a predominantly meat-based diet, rich in red meat and processed meat (e.g. smoked meat, bacon, sausages, cold cuts) has been shown to increase risks of certain cancers, including colon cancer which some studies link to high blood levels of vitamin B12. Meat is also high in vitamin B12 and can account for the high levels of the vitamin.
Lastly, to reach abnormally high blood levels of vitamin B12, a person would have to exhibit a severe deficiency and undergo appropriate supplementation which would likely be achieved via routes such as intravenous or intramuscular preparations. It is not uncommon for vitamin supplements administered via IV, intravenous injections or intramuscular injections to contain preservatives. Preservatives are known for their carcinogenic potential so it would make sense to observe an increased risk of cancer long-term.
What are the benefits of vitamin B12?
Some of the biggest benefits of vitamin B12 include:
- Vitamin B12 boosts the benefits of folic acid and actively helps protect against neural tube defects occurring during pregnancy.
- Studies show supplementation with vitamin B12 (and B9) helps combat carcinogen-induced oxidative stress (source).
- Vitamin B12 supports the production of red blood cells in the bone marrow and helps prevent anemia and associated side effects.
- It is vital for the synthesis of myelin, the protective, insulating coating surrounding the tail of nerve cells. Demyelination, loss of the myelin sheath, is a hallmark of neurodegenerative diseases such as multiple sclerosis.
- Potentially benefits for delaying cognitive decline and improving memory.
- Elevates energy levels by helping cells metabolize fats and proteins, and boosts endurance.
- Combats numbness and tingling in fingers, hands, toes, feet, arms and legs, painful muscle cramps, muscle contractions and spasms.
- Lowers homocysteine levels with benefits for cardiovascular health.
- Benefits for autoimmune diseases, constipation, palpitations, arrhythmia and more.
Vitamin B12 deficiency: signs, symptoms, risks
Without a shadow of a doubt, vitamin B12 is an important source of benefits for health and no human body can function optimally and be healthy without an adequate intake. Vitamin B12 deficiency is prevalent among vegans who do not supplement, and even some categories of vegetarians are at risk for vitamin B12 deficiency, namely vegetarians who do not consume most animal products or in amounts too low to meet their dietary requirements (source 1, source 2). Women of childbearing age, especially women with endometriosis or non-pathological heavy menses also tend to regularly experience a deficiency.
Signs, symptoms and side effects of vitamin B12 deficiency include:
- Low energy levels, tiredness, fatigue and physical weakness, especially muscle weakness.
- Lack of motivation, poor productivity, brain fog, irritability, poor concentration, memory problems.
- Lightheadedness, lethargy, confusion, fainting.
- Low red blood cell and low hemoglobin levels.
- Megaloblastic anemia.
- Pale skin.
- Easy bruising or bleeding e.g. frequent nosebleeds, bleeding gums.
- Cardiovascular problems: palpitations, arrhythmias, rapid heartbeat, breathlessness.
- Digestive symptoms: frequent diarrhea or constipation, stomach pain, poor digestion, sore tongue.
- Neurological symptoms: headaches, poor reflexes, involuntary movements of the muscles such as tingling, numbness and pins and needles sensation.
- Muscle symptoms: muscle weakness, coordination problems leading to balance problems.
- In children: developmental problems.
